An embolus can be any particle comprising a foreign or native material, which enters the vascular system with potential to cause occlusion of blood flow. Emboli can be formed from aggregated fibrin, red blood cells, collagen, cholesterol, plaque, fat, calcified plaque, bubbles, arterial tissue, and/or other miscellaneous fragments. Emboli range in size from 0.01 cubic millimeters (mm3) to 12.5 mm3 (with an approximate mean of 0.80 mm3). Emboli characterization is described further described in reference 1. (1) While some references are cited explicitly in the text, other references are cited in a list at the end of the specification. References listed at the end of the specification are cited with a number of the reference in parentheses. These references are incorporated by reference in their entirety as well as specifically for the particular principle being referenced.
Cardiac Surgery
Each year there are approximately 800,000 cardiac surgical cases which involve cardiopulmonary bypass (CPB) worldwide. (2) Of these cardiac surgical cases, approximately 48,000 suffer stroke and nearly 300,000 experience some neurocognitive disturbance. (3) This is a significant clinical problem. These complications are due in large measure to CPB-generated emboli. The average number of emboli measured by Trans Cranial Doppler (TCD) in patients undergoing cardiopulmonary bypass is 183 (range 3-947). (2) The majority of emboli end up in the very distal cerebral tree, the terminal arterioles and capillaries causing microinfarctions, (i.e., loss of blood to surrounding tissue). (4) Pathological evaluation of affected tissues reveals sausage-shaped arterial dilatations known as SCADs. Cerebral microinfarctions can cause confusion, disturbances of speech, paralysis, visual disturbances, balance disturbances and other neurological deviations. (5) These impairments are frequently short term but can be permanent.
Whether long term or short term, neurocognitive disturbances translate into significant patient care spending. An estimated $750 million dollars is spent annually on hospital care for CPB patients and an additional $500 million on long-term hospice care. (2) The average stay for CPB patients without adverse cerebral outcomes is 8.6 days, while patients with severe adverse outcomes stay an average of 55.8 days. (3 and 6) Estimating the average hospital day care cost at $1500/day, extended stays due to embolic events translate on average into an additional $60,000 per patient. While daunting, this figure still fails to include the social and financial burden placed on family members upon hospital release. In sum, surgically triggered embolic events cause high rates of clinically observed neurological disturbances, decreased quality of life and increased patient care spending.
Cardiac surgical procedures have been correlated directly with neurological injury and stroke due in large measure to the formation of emboli. Emboli can be generated by surgical maneuvers such as cannulation, aortic manipulation, clamping and unclamping. In fact, by some estimates, 60% of the total emboli can be associated with clamp manipulation alone. The average number of emboli measured by Trans Cranial Doppler (TCD) in patients undergoing coronary bypass is 135 (range 0-1377), and in patients undergoing vascular surgery, the average number increases to 1030 (range 18 to 5890). The majority of the emboli end up in the very distal cerebral tree, the terminal arterioles and capillaries causing microinfarcts, (i.e., loss of blood to surrounding tissue).
Furthermore, mortality increased from 7.4% in patients without adverse cerebral outcomes to 30.4% in patients who did have adverse cerebral outcomes. A study conducted in Sweden reviewed 7,000 open heart procedures. Their results with respect to incidence of symptoms as a percentage of all cases are as follows: disturbance of consciousness including slow awakening (1.8%), confusion (5.3%), disturbances of speech (1.3%), paresis (2.0%), visual disturbances (1.0%), balance/coordination disturbances (2.3%), seizures (0.2%) and other neurological deviations (1.8%).
Vascular Surgery
Emboli formation can also create problems in the realm of vascular disease, though in these instances the clinical outcome can be pulmonary embolism (PE). Approximately 600,000 people in the United States suffer from venous thrombi, which could result in a lung embolus. Mortality associated with untreated PE is approximately 30%. (7) While secondary to cardiac surgery, this area represents a Significant clinical indication.
Cardiology and Endovascular Intervention
Other procedures that can result in emboli include, for example, coronary, carotid, and peripheral interventions. (8) In these cases, particulate matter, including, for example, plaque, debris and thrombus, can form emboli distal to the site of intervention. As a result, blood flow to the distal vascular bed is diminished and periprocedural end-organ ischemia and infarction can result. Distal embolization of large particles produced at the time of such interventions as balloon inflation or stent deployment may obstruct large, epicardial vessels, and smaller particles (as little as 15-100 microns) can cause microinfarcts and/or myocardial infarctions and left ventricular dysfunction. (8) Myocardial infarction refers to the death of a section of myocardium or middle layer of the heart muscle. Myocardial infarction can result from at least partial blockage of the coronary artery or its branches. Blockage of capillaries associated with the coronary arteries can result in corresponding microinfarctions/microinfarcs.
Urology and Gastroenterology
Blockage of other body vessels can occur. For example, kidney stones are one of the most painful of the urologic disorders. Kidney stones also represent one of the most common disorders of the urinary tract; it is estimated that more than 1 million cases were diagnosed in 1996. It has also estimated 10 percent of people in the United States will have a kidney stone at some point in their lives. While most kidney stones pass out of the body without any intervention, stones that cause lasting symptoms or other complications require removal. Thus, like the other emboli generated in vascular system, urology could benefit from a devices to remove and resorb calculi in the urinary tract. This calculi is composed of calcium oxalate. Since it is a relatively hard substance, it can cause great pain as it passes through the urinary tract. Such removal is often necessary in cases of obstruction, i.e. embolism.
Emboli and Infection
When foreign material in the stream of flow causes turbulence or low flow, it has been shown that this increases infection rates. Thrombus not only generates emboli, but also increases the risk of infection. (9) Likewise kidney stones can create additional risk for infection.
It is evident that a wide variety of embolic events cause high rates of clinically observed symptoms, decreased quality of life and increased patient care spending.